A pneumatic muscle-driven flexible knee exoskeleton

Abstract

The present application discloses a pneumatic muscle-driven flexible knee exoskeleton, which relates to the fields of intelligent equipment, robots, and wearable equipment. It includes a thigh fixing plate, a calf fixing plate, a bionic joint, and a pneumatic muscle module. The bionic joint is connected between the thigh fixing plate and the calf fixing plate, so that the instantaneous center trajectory between the thigh fixing plate and the calf fixing plate is consistent with the compliance trajectory of the knee. The pneumatic muscle module includes a pneumatic muscle, a first steel wire rope, a second steel wire rope, and a linkage mechanism. The pneumatic muscle is connected to the position on the front of the thigh facing the thigh of the thigh fixing plate. One end of the first steel wire rope is connected to the output end of the pneumatic muscle, and the other end is connected to the linkage mechanism. One end of the second steel wire rope is connected to the linkage mechanism, and the other end is connected to the calf fixing plate. The pneumatic muscle is used to drive the first steel wire rope to move to drive the linkage mechanism to move, and the movement of the linkage mechanism drives the first steel wire rope to be tightened. The flexibility of the knee assist exoskeleton is improved, and the matching degree with joint movement is high.

Description

Technical Field

[0001] The present invention relates to a pneumatic muscle-driven flexible knee exoskeleton, belonging to the fields of intelligent equipment, robots, and wearable equipment. Background Art

[0002] Current rigid exoskeleton systems have problems such as large system weight, insufficiently compliant assistance, poor flexibility and wearing adaptability, and it is difficult to meet the requirements of adapting to complex environments, multi-tasks, mobility, etc. Conducting research on flexible exoskeleton technology is an effective technical approach to solve the above problems and the future development trend of exoskeletons.

[0003] Currently, most research on flexible exoskeletons focuses on control compliance, and there is less research on the flexibility of the exoskeleton body. This project uses pneumatic muscles as flexible drive sources, and through high integration with a humanoid knee joint mechanism, a pneumatic drive system, sensors, a controller, etc., it realizes effective compliant assistance for wearers in various motion modes such as walking, going up and down stairs. This flexible drive technology can also be applied to various scenarios that require assistance, such as light mobility, material handling, outdoor sports protection, and assisting the elderly and disabled in walking. Summary of the Invention

[0004] The technical problem solved by the present invention is: overcoming the deficiencies of the prior art, providing a flexible assistive knee exoskeleton solution based on pneumatic muscles with a human knee joint force generation method, and solving the problems of poor compliance of the exoskeleton body, insufficient contraction rate of pneumatic muscles when used in exoskeletons to meet the human motion space, and mismatch of the human-machine joint motion axes.

[0005] The technical solution of the present invention is:

[0006] A pneumatic muscle-driven flexible knee exoskeleton, comprising:

[0007] A thigh fixing plate for connecting to the outer side of the thigh;

[0008] A calf fixing plate for connecting to the outer side of the calf;

[0009] A bionic joint connected between the thigh fixing plate and the calf fixing plate, and the bionic joint is a four-bar linkage mechanism of a joint, so that the instantaneous center locus of the four-bar linkage mechanism of the joint is consistent with the instantaneous center locus of the human knee joint;

[0010] The pneumatic muscle module includes a pneumatic muscle, a first steel wire rope, a second steel wire rope, and a linkage mechanism. The pneumatic muscle is connected to the front position of the thigh fixing plate to simulate the layout of the quadriceps femoris of the human body. One end of the first steel wire rope is connected to the output end of the pneumatic muscle, and the other end is connected to the linkage mechanism. One end of the second steel wire rope is connected to the linkage mechanism, and the other end bypasses the knee joint position and is connected to the calf fixing plate. The pneumatic muscle is used to drive the first steel wire rope to move, thereby driving the linkage mechanism to move, and the movement of the linkage mechanism drives the second steel wire rope to be tightened.

[0011] The overall scheme uses the pneumatic muscle to pull the first steel wire rope and the second steel wire rope to drive the calf fixing plate to move relative to the thigh fixing plate to simulate the movement of the human body where the quadriceps femoris pulls the calf tibia through the patellar ligament and tendon, which completely imitates the force generation mode of the human knee joint.

[0012] The linkage mechanism is a two-stage deceleration linkage device to achieve the purpose of reducing force and increasing stroke and supplementing the contraction rate of the pneumatic muscle. The linkage mechanism includes a first guide wheel, a small transmission wheel, and a large transmission wheel rotatably connected to the thigh fixing plate. One end of the first steel wire rope is connected to the groove of the small transmission wheel, then bypasses the rope groove of the small transmission wheel and the first guide wheel, and the other end is connected to the output end of the pneumatic muscle. The small transmission wheel and the large transmission wheel are connected by a connecting device so that the small transmission wheel drives the large transmission wheel to rotate. One end of the second steel wire rope is connected to the groove of the large transmission wheel.

[0013] The connecting device includes a large gear and a small gear. The large gear and the small transmission wheel are coaxial and rotate synchronously. The small gear and the large transmission wheel are coaxial and rotate synchronously. The small gear meshes with the large gear.

[0014] The diameter of the small transmission wheel is smaller than that of the large transmission wheel, and the diameter of the large gear is larger than that of the small gear.

[0015] A second guide wheel is rotatably connected to the end of the thigh fixing plate close to the calf fixing plate, and a fourth guide wheel is rotatably connected to the end of the calf fixing plate close to the second fixing plate. The second guide wheel and the fourth guide wheel are used to guide the second steel wire rope.

[0016] Two pneumatic muscles are provided. The two pneumatic muscles are arranged on both sides of the linkage mechanism. An output end fixing frame is connected between the output ends of the two pneumatic muscles. The end of the first steel wire rope is connected to the output end fixing frame through a steel wire rope pre-tightening mechanism.

[0017] The wire rope pre-tightening mechanism includes a connecting block, an adjusting screw, and a fastening screw. The end of the first wire rope is connected to the connecting block. The connecting block is provided with a kidney-shaped hole. The fastening screw passes through the kidney-shaped hole and is threadedly connected to the output end fixing bracket. The adjusting screw is threadedly connected to the output end fixing bracket and abuts against its upper surface. The moving direction of the output end of the pneumatic muscle is parallel to the axis of the adjusting screw and the length direction of the kidney-shaped hole. The two side surfaces of the connecting block and the grooves of the output end fixing bracket are mutually guiding. When adjusting the tightness, the adjusting screw is manually rotated to abut against the upper surface of the output end fixing bracket to generate a reverse movement to pre-tighten the wire rope. After adjusting the tightness, the connecting block is fixed by the fastening screw to complete the pre-tightening process. Just operate in the reverse direction to loosen it.

[0018] The end of the second wire rope at the calf is provided with a pre-tightening mechanism for tensioning the pneumatic muscle. The pre-tightening mechanism includes a constant force spring, a sliding connector, a tension sensor, a wire rope connector, a slide rail, a constant force spring shaft, a constant force spring bracket, and a slide rail bracket; the constant force spring is installed on the constant force spring shaft, and its extended end is fixed in the groove of the sliding connector; the sliding connector is threadedly connected to the tension sensor, and its two side lugs are placed on the slide rail, and the sliding connector can slide along the slide rail; the tension sensor is placed between the wire rope connector and the sliding connector and is threadedly connected to both; the end of the second wire rope is fixed to the wire rope connector; one end of the slide rail is hinged to the constant force spring shaft, and the other end is fixed to the slide rail bracket. When the pneumatic muscle works normally, the lugs of the sliding connector abut against the upper part of the groove of the slide rail, and the tension sensor also works normally. At this time, the constant force spring is in a stretched state; when the pneumatic muscle works abnormally and becomes slack, the restoring force of the constant force spring can keep the pneumatic muscle taut.

[0019] Two bionic joints are provided. The two bionic joints are respectively located on both sides of the thigh fixing plate and the calf fixing plate facing the knee. The bionic joint includes a thigh rod, a calf rod, a first driven rod, and a second driven rod. The thigh rod is fixedly connected to the thigh fixing plate, the calf rod is fixedly connected to the calf fixing plate, and both ends of the first driven rod and the second driven rod are hinged to the thigh fixing plate and the calf fixing plate respectively.

[0020] The pneumatic muscle is connected with a pneumatic drive and control system. The pneumatic drive and control system includes a controller, a pump, a buffer gas cylinder, and an air pipeline. The controller is used to control the pump to generate the required air pressure and perform air pressure following. The pump is connected to the buffer gas cylinder, the buffer gas cylinder is communicated with the air pipeline, and the air pipeline is connected to the pneumatic muscle.

[0021] In summary, the present application at least includes the following beneficial technical effects:

[0022] (1) A general scheme of a pneumatic muscle knee flexible exoskeleton with a human knee joint-like force generation method is proposed, and the force transmission method is more anthropomorphic.

[0023] (2) It is driven by pneumatic muscles, which improves the flexibility of the exoskeleton. Through the parallel connection of pneumatic muscles and the two-stage deceleration linkage mechanism, its contraction rate is greatly increased, meeting the requirements of the human-machine movement space.

[0024] (3) Through the design of a humanoid knee joint mechanism, its instantaneous center trajectory matches the movement of the human knee joint, improving the human-machine coordination. Brief Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the overall structure of a flexible knee exoskeleton driven by pneumatic muscles in an embodiment of the present application.

[0026] Figure 2 It is a schematic diagram of the structure of the linkage mechanism in an embodiment of the present application;

[0027] Figure 3 It is a cross-sectional view of the winding paths of the first steel wire rope and the second steel wire rope in an embodiment of the present application;

[0028] Figure 4 It is a partial front view of the winding of the first steel wire rope and the second steel wire rope in an embodiment of the present application;

[0029] Figure 5 It is a front view of the winding of the first steel wire rope and the second steel wire rope in an embodiment of the present application

[0030] Figure 6 It is a schematic diagram of the structure of the bionic joint in an embodiment of the present application;

[0031] Figure 7 It is a schematic diagram of the structure of the pre-tightening mechanism on the calf fixing plate in an embodiment of the present application;

[0032] Figure 8 It is a schematic diagram of the structure of the wire rope pre-tightening mechanism connected to the wire rope pre-tightening mechanism in an embodiment of the present application;

[0033] Figure 9 It is a schematic diagram of the structure of the pneumatic drive and control system in an embodiment of the present application.

[0034] Description of the reference numerals: 1. Pneumatic muscle module; 11. Pneumatic muscle; 12. First steel wire rope; 13. Second steel wire rope; 14. First guide wheel; 15. Small transmission wheel; 16. Large transmission wheel; 17. Large gear; 18. Small gear;

[0035] 2. Bionic joint; 21. Thigh rod; 22. First driven rod; 23. Calf rod; 24. Second driven rod;

[0036] 3. Thigh fixing plate; 31. Output end fixing bracket; 311. Connecting block; 312. Adjusting screw; 313. Fastening screw; 314. Second guide wheel; 315. Third guide wheel; 316. Fourth guide wheel; 32. Top fixing bracket;

[0037] 4. Calf fixing plate; 41. Constant force spring; 42. Sliding part; 43. Tension sensor; 44. Steel wire rope connecting piece; 45. Slide rail; 46. Constant force spring shaft; 47. Constant force spring bracket; 48. Slide rail bracket;

[0038] 51. Controller; 52. Pump; 53. Buffer gas cylinder; 54. Air pipeline. Specific implementation manner

[0039] The following further describes the present application in detail with reference to the accompanying drawings and specific embodiments:

[0040] The embodiment of the present application discloses a pneumatic muscle-driven flexible knee exoskeleton, as Figure 1 and Figure 2 shown, including a thigh fixing plate 3, a calf fixing plate 4, a bionic joint 2, a pneumatic muscle module 1, and a pneumatic drive and control system 5. The thigh fixing plate 3 is connected to the outer side of the thigh, and the calf fixing plate 4 is connected to the outer side of the calf. The bionic joint 2 is connected between the thigh fixing plate 3 and the calf fixing plate 4 so that the instantaneous center trajectory between the thigh fixing plate 3 and the calf fixing plate 4 is consistent with the instantaneous center trajectory of the knee. The pneumatic drive and control system 5 provides driving power for the pneumatic muscle module 1, and the pneumatic muscle module 1 provides driving force for the calf straightening process. The thigh fixing plate 3 provides fixed support for the pneumatic muscle module 1 and is connected to the calf fixing plate 4 through the bionic joint 2. The thigh fixing plate 3 and the calf fixing plate 4 are fixed to the human leg to reduce the pressure between the human and the machine.

[0041] The pneumatic muscle module 1 includes a pneumatic muscle 11, a first steel wire rope 12, a second steel wire rope 13, and a linkage mechanism.

[0042] Among them, the pneumatic muscle 11 is connected to the position on the front of the thigh opposite to the thigh fixing plate 3. In this embodiment, two pneumatic muscles 11 are provided. The two starting muscles 11 are connected in parallel on both sides of the thigh fixing plate 3 and are respectively arranged on both sides of the linkage mechanism. The two pneumatic muscles 11 are fixedly connected to the thigh fixing plate 3 through the top fixing bracket 32. The two pneumatic muscles 11 are respectively arranged on both sides of the linkage mechanism. An output end fixing bracket 31 is connected between the output ends of the two pneumatic muscles 11. The pneumatic muscle 11 is a cylinder.

[0043] Such as Figure 2As shown, the linkage mechanism is a two-stage deceleration linkage device, which realizes the purpose of reducing force and increasing stroke to supplement the contraction rate of the pneumatic muscle. The linkage mechanism includes a small transmission wheel 15, a large transmission wheel 16, a large gear 17, a small gear 18, and a first guide wheel 14 rotatably connected to the thigh fixing plate 3. Among them, the small pulley 15 and the large gear 17 are coaxial and rotate synchronously, the small gear 18 and the large pulley 16 are coaxial and rotate synchronously, and the large gear 17 and the small gear 18 are kept meshed. One end of the first steel wire rope 12 is fixed in the groove of the small pulley 15, passes around the rope groove of the small pulley 15 and the first guide wheel 14, and the other end is connected to the groove of the connecting block 311 fixedly connected to the output end of the pneumatic muscle 11. The diameter of the large gear 17 is larger than that of the small gear 18, and the diameter of the small transmission wheel 15 is smaller than that of the large transmission wheel 16. A second guide wheel 314 is rotatably connected to the end of the thigh fixing plate 3 close to the calf fixing plate 4. A third guide wheel 315 is also rotatably connected between the large transmission wheel 16 and the second guide wheel 314 on the thigh fixing plate 3. A fourth guide wheel 316 is rotatably connected to the end of the calf fixing plate 4 close to the second fixing plate. The second guide wheel 314 and the fourth guide wheel 316 are used to guide the second steel wire rope 13.

[0044] As Figure 3 , Figure 4 and Figure 5 shown, one end of the first steel wire rope 12 is fixed to the output end fixing frame 31. After passing through the first guide wheel 14, it is wound and fixed on the small transmission wheel 15. One end of the second steel wire rope 13 is fixed on the large transmission wheel, and after passing through the third guide wheel 315, the second guide wheel 314 and the fourth guide wheel 316, the other end is connected to the calf fixing plate 4. When the piston rod of the pneumatic muscle 11 retracts, it drives the output end fixing frame 31 to move. The output end fixing frame 31 pulls the first steel wire rope 12 to unwind. The first steel wire rope 12 pulls the small transmission wheel 15 to rotate. The small transmission wheel 15 drives the large transmission wheel 16 to rotate through the meshing of the small gear 18 and the large gear 17. Thus, the rotation of the large transmission wheel 16 winds the second steel wire rope 13 around the circumference of the large transmission wheel 16. The second steel wire rope 13 pulls the calf fixing plate 4 upward, thereby generating a straightening force on the human calf.

[0045] Through the above structure, the linkage mechanism can amplify the stroke of the pneumatic muscle 11, ensuring that the second steel wire rope 13 has enough pulling stroke for the calf fixing plate 4.

[0046] As Figure 8As shown, the second steel wire rope 13 is connected to the output end fixing bracket 31 through a steel wire rope pre-tightening mechanism. The steel wire rope pre-tightening mechanism includes a connecting block 311, an adjusting screw 312, and a fastening screw 313. The end of the first steel wire rope 12 is connected to the connecting block 311. The connecting block 311 is provided with a waist-shaped hole. The fastening screw 313 passes through the waist-shaped hole and is threadedly connected to the output end fixing bracket 31. The adjusting screw 312 is threadedly connected to the output end fixing bracket 31 and abuts against its upper surface. The moving direction of the output end of the pneumatic muscle 11 is parallel to the axis of the adjusting screw 312 and the length direction of the waist-shaped hole. The two side surfaces of the connecting block 311 and the groove of the output end fixing bracket 31 are mutually guiding. When adjusting the tightness, manually rotate the adjusting screw 312 to abut against the upper surface of the output end fixing bracket 31 to generate a reverse movement to pre-tighten the steel wire rope. After adjusting the tightness, then fix the connecting block 311 through the fastening screw 313 to complete the pre-tightening process. Reverse operation can be carried out when loosening.

[0047] Loosen the fastening screw 313, and then rotate the fastening screw 313. The fastening screw 313 drives the relative movement between the connecting block 311 and the output end fixing bracket 31. Specifically, the connecting block 311 and the output end fixing bracket 31 move along the length direction of the waist-shaped hole, and the tension degree of the first steel wire rope 12 changes, realizing the adjustment of the tension degree of the first steel wire rope 12.

[0048] As Figure 7 As shown, a pre-tightening mechanism for tensioning the second steel wire rope 13 is provided between the calf fixing plate 4 and the second steel wire rope 13. The pre-tightening mechanism includes a constant force spring 41, a sliding part 42, a tension sensor 43, a steel wire rope connecting piece 44, a slide rail 45, a constant force spring shaft 46, a constant force spring frame 47, and a slide rail frame 48. The constant force spring 41 is installed on the constant force spring shaft 46, and its extending end is fixed in the groove of the sliding connecting piece 42; the sliding connecting piece 42 is threadedly connected to the tension sensor 43, and its two side ears are placed on the slide rail 45, and the sliding connecting piece 42 can slide along the slide rail 45; the tension sensor 43 is placed between the steel wire rope connecting piece 44 and the sliding connecting piece 42 and is threadedly connected to both; the end of the second steel wire rope 13 is fixed to the steel wire rope connecting piece 44; one end of the slide rail 45 is hinged to the constant force spring shaft 46, and the other end is fixed to the slide rail frame 48. When the pneumatic muscle works normally, the side ear of the sliding connecting piece 42 abuts against the upper part of the groove of the slide rail 45, and the tension sensor 43 also works normally. At this time, the constant force spring 41 is in a stretched state; when the pneumatic muscle works abnormally and becomes slack, the restoring force of the constant force spring 41 can keep the pneumatic muscle 11 taut.

[0049] During normal use, the sliding part 42 is always tightened at the end of the chute by the second steel wire rope 13. When the response of the pneumatic muscle 11 cannot keep up, the pneumatic muscle 11 fails, etc., the second steel wire rope 13 becomes slack. At this time, the constant force spring 41 pulls the sliding part 42 to move, so that the second steel wire rope 13 remains taut.

[0050] As Figure 6 shown, two bionic joints 2 are provided. The two bionic joints 2 are respectively located on both sides of the thigh fixing plate 3 and the calf fixing plate 4 facing the knee. The bionic joint 2 includes a thigh rod 21, a calf rod 23, a first driven rod 22 and a second driven rod 24. The thigh rod 21 is fixedly connected to the thigh fixing plate 3, the calf rod 23 is fixedly connected to the calf fixing plate 4, and both ends of the first driven rod 22 and the second driven rod 24 are hinged to the thigh fixing plate 3 and the calf fixing plate 4 respectively. An active rod is formed between the hinge point of the first driven rod 22 and the calf rod 23 and the hinge point of the second driven rod 24 and the calf rod 23. A base part is formed between the hinge point of the first driven rod 22 and the thigh rod 21 and the hinge point of the second driven rod 24 and the thigh rod 21.

[0051] When the human calf drives the calf rod 23 to rotate, the first driven rod 22 and the second driven rod 24 follow the calf rod 23 to rotate. The instantaneous center locus of the four-bar mechanism of the bionic joint 2 is similar to the human knee joint locus, thereby improving the human-machine motion matching.

[0052] As Figure 9 shown, the pneumatic drive and control system includes a controller 51, a pump 52, a buffer gas cylinder 53 and a gas pipeline 54. The controller 51 is used to control the pump 52 to generate the required air pressure and perform air pressure following. The pump 52 is connected to the buffer gas cylinder 53. The buffer gas cylinder 53 is communicated with the gas pipeline 54. The gas pipeline 54 is connected to the pneumatic muscle 11. When inflating, the gas is filled into the pneumatic muscle 11 from the pump 52 through the buffer gas cylinder 53 and the gas pipeline 54, and then it starts to contract and work.

[0053] The implementation principle of this application is as follows:

[0054] The output end fixing bracket 31 of the pneumatic muscle 11 retracts and moves. The output end fixing bracket 31 pulls the first steel wire rope 12 to unwind. The first steel wire rope 12 pulls the small transmission wheel 15 to rotate. The small transmission wheel 15 drives the large transmission wheel 16 to rotate through the meshing of the small gear 18 and the large gear 17. Thus, the rotation of the large transmission wheel 16 winds the second steel wire rope 13 around the circumference of the large transmission wheel 16. The second steel wire rope 13 pulls the calf fixing plate 4 upward, and then generates a straightening force on the human calf.

[0055] The knee exoskeleton of this application provides assistance for the straightening of the calf in the form of pushing, which is more in line with the driving form of the human leg. And further by setting up a linkage mechanism, the stroke of the pneumatic muscle 11 is amplified, so that the whole structure can meet the high stroke requirements satisfied by the front drive. Combined with the screw rod structure of the bionic joint 2 of this application, the problems of poor compliance and mismatched joint movement of the knee assist exoskeleton are solved.

[0056] Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims of the present invention.

Claims

1. A pneumatic muscle-driven flexible knee exoskeleton, characterized in that: It includes a thigh fixing plate (3) for connecting to the outer side of the thigh; a calf fixing plate (4) for connecting to the outer side of the calf; a bionic joint (2) connected between the thigh fixing plate (3) and the calf fixing plate (4), and the bionic joint (2) is a four-bar linkage mechanism of the joint, so that the instantaneous center locus of the four-bar linkage mechanism of the joint is consistent with the instantaneous center locus of the human knee joint; a pneumatic muscle module (1), including a pneumatic muscle (11), a first steel wire rope (12), a second steel wire rope (13), and a linkage mechanism; the pneumatic muscle (11) is connected to the front position of the thigh fixing plate (3) to simulate the layout of the human quadriceps femoris. One end of the first steel wire rope (12) is connected to the output end of the pneumatic muscle (11), and the other end is connected to the linkage mechanism. One end of the second steel wire rope (13) is connected to the linkage mechanism, and the other end bypasses the knee joint position and is connected to the calf fixing plate (4). The pneumatic muscle (11) is used to drive the first steel wire rope (12) to move to drive the linkage mechanism to move, and the movement of the linkage mechanism drives the second steel wire rope (13) to be tightened; The pneumatic muscle (11) pulls the first steel wire rope (12) and the second steel wire rope (13) to drive the calf structure to move, so as to simulate the movement of the human body that the quadriceps femoris pulls the calf tibia through the patellar ligament and tendon, and completely imitates the force generation of the human knee joint.

2. The pneumatic muscle-driven flexible knee exoskeleton according to claim 1, characterized in that: The linkage mechanism is a two-stage deceleration linkage device to achieve the purpose of reducing force and increasing stroke and supplementing the contraction rate of the pneumatic muscle; the linkage mechanism includes a first guide wheel (14), a small transmission wheel (15), and a large transmission wheel (16) rotatably connected to the thigh fixing plate (3). One end of the first steel wire rope (12) is connected to the groove of the small transmission wheel (15), then bypasses the rope groove of the small transmission wheel (15) and the first guide wheel (14), and the other end is connected to the output end of the pneumatic muscle (11). The small transmission wheel (15) and the large transmission wheel (16) are connected by a connecting device, so that the small transmission wheel (15) drives the large transmission wheel (16) to rotate, and one end of the second steel wire rope (13) is connected to the groove of the large transmission wheel (16).

3. The pneumatic muscle-driven flexible knee exoskeleton according to claim 2, characterized in that: The connecting device includes a large gear (17) and a small gear (18). The large gear (17) and the small transmission wheel (15) are coaxial and rotate synchronously. The small gear (18) and the large transmission wheel (16) are coaxial and rotate synchronously. The small gear (18) meshes with the large gear (17).

4. The pneumatic muscle-driven flexible knee exoskeleton according to claim 3, characterized in that: The diameter of the small transmission wheel (15) is smaller than the diameter of the large transmission wheel (16), and the diameter of the large gear (17) is larger than the diameter of the small gear (18); A second guide wheel (314) is rotatably connected to the end of the thigh fixing plate (3) close to the calf fixing plate (4), and a fourth guide wheel (316) is rotatably connected to the end of the calf fixing plate (4) close to the second fixing plate. The second guide wheel (314) and the fourth guide wheel (316) are used to guide the second steel wire rope (13).

5. A pneumatic muscle-driven flexible knee joint exoskeleton according to any one of claims 2-4, characterized in that: Two pneumatic muscles (11) are provided, and the two pneumatic muscles (11) are connected in parallel on both sides of the thigh fixing plate (3). An output end fixing frame (31) is connected between the output ends of the two pneumatic muscles (11). The end of the first steel wire rope (12) is connected to the output end fixing frame (31) through a steel wire rope pre-tightening mechanism.

6. A pneumatic muscle-driven flexible knee joint exoskeleton according to claim 5, characterized in that: The steel wire rope pre-tightening mechanism includes a connecting block (311), an adjusting screw (312) and a fastening screw (313). The end of the first steel wire rope (12) is connected to the connecting block (311). The connecting block (311) is provided with a kidney-shaped hole. The fastening screw (313) passes through the kidney-shaped hole and is threadedly connected to the output end fixing frame (31). The adjusting screw (312) is threadedly connected to the output end fixing frame (31) and abuts against its upper surface. The moving direction of the output end of the pneumatic muscle (11) is parallel to the axis of the adjusting screw (312) and the length direction of the kidney-shaped hole. The two side surfaces of the connecting block (311) are mutually guided with the groove of the output end fixing frame (31); when adjusting the tightness, the adjusting screw (312) is manually rotated to abut against the upper surface of the output end fixing frame (31) to generate opposite-direction movement to pre-tighten the steel wire rope; after adjusting the tightness, the connecting block (311) is fixed by the fastening screw (313) to complete the pre-tightening process; when loosening, just operate in the reverse direction.

7. A pneumatic muscle-driven flexible knee joint exoskeleton according to claim 1, characterized in that: The end of the second steel wire rope (13) at the calf is provided with a pre-tightening mechanism for tensioning the pneumatic muscle (11). The pre-tightening mechanism includes a constant force spring (41), a sliding connector (42), a tension sensor (43), a wire rope connector (44), a slide rail (45), a constant force spring shaft (46), a constant force spring bracket (47) and a slide rail bracket (48); the constant force spring (41) is installed on the constant force spring shaft (46), and its extended end is fixed in the groove of the sliding connector (42); the sliding connector (42) is threadedly connected to the tension sensor (43), and its two side lugs are placed on the slide rail (45), and the sliding connector (42) can slide along the slide rail (45); the tension sensor (43) is placed between the wire rope connector (44) and the sliding connector (42) and is threadedly connected to both of them; the end of the second steel wire rope (13) is fixed to the wire rope connector (44); one end of the slide rail (45) is hinged to the constant force spring shaft (46), and the other end is fixed to the slide rail bracket (48); when the pneumatic muscle works normally, the lugs of the sliding connector (42) abut against the upper part of the groove of the slide rail (45), and the tension sensor (43) also works normally. At this time, the constant force spring (41) is in a stretched state; when the pneumatic muscle works abnormally and becomes slack, the restoring force of the constant force spring (41) can keep the pneumatic muscle (11) tensioned.

8. A pneumatic muscle-driven flexible knee joint exoskeleton according to claim 1, characterized in that: Two bionic joints (2) are provided. The two bionic joints (2) are respectively located on both sides of the thigh fixing plate (3) and the calf fixing plate (4) facing the knee. The bionic joint (2) includes a thigh rod (21), a calf rod (23), a first driven rod (22) and a second driven rod (24). The thigh rod (21) is fixedly connected to the thigh fixing plate (3), the calf rod (23) is fixedly connected to the calf fixing plate (4), and both ends of the first driven rod (22) and the second driven rod (24) are hinged to the thigh fixing plate (3) and the calf fixing plate (4) respectively.

9. A pneumatic muscle-driven flexible knee joint exoskeleton according to claim 1, characterized in that: The pneumatic muscle (11) is connected with a pneumatic drive and control system. The pneumatic drive and control system includes a controller (51), a pump (52), a buffer gas cylinder (53) and an air pipeline (54). The controller (51) is used to control the pump (52) to generate the required air pressure and perform air pressure following. The pump (52) is connected to the buffer gas cylinder (53), the buffer gas cylinder (53) is communicated with the air pipeline (54), and the air pipeline (54) is connected to the pneumatic muscle (11).

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